Enzymatic properties and expression patterns of five extracellular lipases of Fusarium graminearum in vitro

A polylactic acid degrading lipase from Bacillus safensis: Characterization and structural analysis

A polylactic acid degrading triacylglycerol lipase (TGL) was identified from Bacillus safensis based on genome annotation and validated by real-time quantitative PCR. TGL displayed optimal activity at pH 9.0 and 55 °C. It maintained stability at pH 9.0 and temperatures 45 °C. The activity of TGL was found to benefit from the presence of potassium sodium ions, and low concentrations of Triton X-100. The TGL could erode the surface of polylactic acid films and increase its hydrophilicity. The hydrolysis products of polylactic acid by TGL were lactate monomer and dimer. TGL contains a classical catalytic triad structure of lipase (Ser77, Asp133, and His156) and an Ala-X-Ser-X-Gly sequence. Compared with some lipases produced by the same genus Bacillus, TGL is highly conserved in its amino acid sequence, mainly reflected in the amino acid residues that exercise the enzyme activity, including the catalytic activity center and the substrate binding sites.

Spray-induced gene silencing to identify powdery mildew gene targets and processes for powdery mildew control

Spray-induced gene silencing (SIGS) is an emerging tool for crop pest protection. It utilizes exogenously applied double-stranded RNA to specifically reduce pest target gene expression using endogenous RNA interference machinery. In this study, SIGS methods were developed and optimized for powdery mildew fungi, which are widespread obligate biotrophic fungi that infect agricultural crops, using the known azole-fungicide target cytochrome P450 51 (CYP51) in the Golovinomyces orontii-Arabidopsis thaliana pathosystem. Additional screening resulted in the identification of conserved gene targets and processes important to powdery mildew proliferation: apoptosis-antagonizing transcription factor in essential cellular metabolism and stress response; lipid catabolism genes lipase a, lipase 1, and acetyl-CoA oxidase in energy production; and genes involved in manipulation of the plant host via abscisic acid metabolism (9-cis-epoxycarotenoid dioxygenase, xanthoxin dehydrogenase, and a putative abscisic acid G-protein coupled receptor) and secretion of the effector protein, effector candidate 2. Powdery mildew is the dominant disease impacting grapes and extensive powdery mildew resistance to applied fungicides has been reported. We therefore developed SIGS for the Erysiphe necator-Vitis vinifera system and tested six successful targets identified using the G. orontii-A. thaliana system. For all targets tested, a similar reduction in powdery mildew disease was observed between systems. This indicates screening of broadly conserved targets in the G. orontii-A. thaliana pathosystem identifies targets and processes for the successful control of other powdery mildew fungi. The efficacy of SIGS on powdery mildew fungi makes SIGS an exciting prospect for commercial powdery mildew control.

Genetic and Transcriptional Regulatory Mechanisms of Lipase Activity in the Plant Pathogenic Fungus Fusarium graminearum

Lipases, which catalyze the hydrolysis of long-chain triglycerides, diglycerides, and monoglycerides into free fatty acids and glycerol, participate in various biological pathways in fungi. In this study, we examined the biological functions and regulatory mechanisms of fungal lipases via two approaches. First, we performed a systemic functional characterization of 86 putative lipase-encoding genes in the plant-pathogenic fungus Fusarium graminearum. The phenotypes were assayed for vegetative growth, asexual and sexual reproduction, stress responses, pathogenicity, mycotoxin production, and lipase activity. Most mutants were normal in the assessed phenotypes, implying overlapping roles for lipases in F. graminearum. In particular, FgLip1 and Fgl1 were revealed as core extracellular lipases in F. graminearum. Second, we examined the lipase activity of previously constructed transcription factor (TF) mutants of F. graminearum and identified three TFs and one histone acetyltransferase that significantly affect lipase activity. The relative transcript levels of FgLIP1 and FGL1 were markedly reduced or enhanced in these TF mutants. Among them, Gzzc258 was identified as a key lipase regulator that is also involved in the induction of lipase activity during sexual reproduction. To our knowledge, this study is the first comprehensive functional analysis of fungal lipases and provides significant insights into the genetic and regulatory mechanisms underlying lipases in fungi. IMPORTANCE Fusarium graminearum is an economically important plant-pathogenic fungus that causes Fusarium head blight (FHB) on wheat and barley. Here, we constructed a gene knockout mutant library of 86 putative lipase-encoding genes and established a comprehensive phenotypic database of the mutants. Among them, we found that FgLip1 and Fgl1 act as core extracellular lipases in this pathogen. Moreover, several putative transcription factors (TFs) that regulate the lipase activities in F. graminearum were identified. The disruption mutants of F. graminearum-lipase regulatory TFs all showed defects in sexual reproduction, which implies a strong relationship between sexual development and lipase activity in this fungus. These findings provide valuable insights into the genetic mechanisms regulating lipase activity as well as its importance to the developmental stages of this plant-pathogenic fungus.

Structural features, temperature adaptation and industrial applications of microbial lipases from psychrophilic, mesophilic and thermophilic origins

Microbial lipases are very prominent biocatalysts because of their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. Here microbial lipases from different origins (psychrophiles, mesophiles, and thermophiles) have been reviewed. This review emphasizes an update of structural diversity in temperature adaptation and industrial applications, of psychrophilic, mesophilic, and thermophilic lipases. The microbial origins of lipases are logically dynamic, proficient, and also have an extensive range of industrial uses with the manufacturing of altered molecules. It is therefore of interest to understand the molecular mechanisms of adaptation to temperature in occurring lipases. However, lipases from extremophiles (psychrophiles, and thermophiles) are widely used to design biotransformation reactions with higher yields, fewer byproducts, or useful side products and have been predicted to catalyze those reactions also, which otherwise are not possible with the mesophilic lipases. Lipases as a multipurpose biological catalyst have given a favorable vision in meeting the needs of several industries such as biodiesel, foods, and drinks, leather, textile, detergents, pharmaceuticals, and medicals.

Biochemical characterization of an alkaline and detergent-stable Lipase from Fusarium annulatum Bugnicourt strain CBS associated with olive tree dieback

This work describes a novel extracellular lipolytic carboxylester hydrolase named FAL, with lipase and phospholipase A1 (PLA1) activity, from a newly isolated filamentous fungus Ascomycota CBS strain, identified as Fusarium annulatum Bunigcourt. FAL was purified to about 62-fold using ammonium sulphate precipitation, Superdex® 200 Increase gel filtration and Q-Sepharose Fast Flow columns, with a total yield of 21%. The specific activity of FAL was found to be 3500 U/mg at pH 9 and 40°C and 5000 U/mg at pH 11 and 45°C, on emulsions of triocanoin and egg yolk phosphatidylcholine, respectively. SDS-PAGE and zymography analysis estimated the molecular weight of FAL to be 33 kDa. FAL was shown to be a PLA1 with a regioselectivity to the sn-1 position of surface-coated phospholipids esterified with α-eleostearic acid. FAL is a serine enzyme since its activity on triglycerides and phospholipids was completely inhibited by the lipase inhibitor Orlistat (40 μM). Interestingly, compared to Fusarium graminearum lipase (GZEL) and the Thermomyces lanuginosus lipase (Lipolase®), this novel fungal (phospho)lipase showed extreme tolerance to the presence of non-polar organic solvents, non-ionic and anionic surfactants, and oxidants, in addition to significant compatibility and stability with some available laundry detergents. The analysis of washing performance showed that it has the capability to efficiently eliminate oil-stains. Overall, FAL could be an ideal choice for application in detergents.

Extracellular vesicles isolated from dsRNA-sprayed barley plants exhibit no growth inhibition or gene silencing in Fusarium graminearum

Numerous reports have shown that incorporating a double-stranded RNA (dsRNA)-expressing transgene into plants or applying dsRNA by spraying it onto their leaves successfully protects them against invading pathogens exploiting the mechanism of RNA interference (RNAi). How dsRNAs or siRNAs are transferred between donor host cells and recipient fungal cells is largely unknown. It is speculated that plant extracellular vesicles (EVs) function as RNA shuttles between plants and their pathogens. Recently, we found that EVs isolated from host-induced gene silencing (HIGS) or spray-induced gene silencing (SIGS) plants contained dsRNA-derived siRNAs. In this study, we evaluated whether isolated EVs from dsRNA-sprayed barley (Hordeum vulgare) plants affected the growth of the phytopathogenic ascomycete Fusarium graminearum. Encouraged by our previous finding that dropping barley-derived EVs on F. graminearum cultures caused fungal stress phenotypes, we conducted an in vitro growth experiment in microtiter plates where we co-cultivated F. graminearum with plant EVs isolated from dsRNA-sprayed barley leaves. We observed that co-cultivation of F. graminearum macroconidia with barley EVs did not affect fungal growth. Furthermore, plant EVs containing SIGS-derived siRNA appeared not to affect F. graminearum growth and showed no gene silencing activity on F. graminearum CYP51 genes. Based on our findings, we concluded that either the amount of SIGS-derived siRNA was insufficient to induce target gene silencing in F. graminearum, indicating that the role of EVs in SIGS is minor, or that F. graminearum uptake of plant EVs from liquid cultures was inefficient or impossible.

Enantioselective Effect of Flutriafol on Growth, Deoxynivalenol Production, and TRI Gene Transcript Levels in Fusarium graminearum

In recent years, deoxynivalenol (DON) has frequently been detected in wheat grains and their products. The enantioselective impact of flutriafol on the growth and DON biosynthesis of Fusarium graminearum was investigated in relation to water activity (α_w, 0.97 and 0.99) and temperature (20, 25, and 30 °C) on the wheat-based medium. R-(-)-flutriafol exhibited higher bioactivity than S-(+)-flutriafol and Rac-flutriafol under the above conditions. Flutriafol enantiomers reduced or stimulated DON biosynthesis depending on α_w. DON levels were negligible after 14 or 7 days of incubation times under 0.97 and 0.99 a_w, respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses showed that the expression levels of trichothecene biosynthetic (TRI) genes of F. graminearum under 0.97 a_w were significantly higher than those under 0.99 a_w. In addition, R-(-)-flutriafol can induce more TRI gene expression than S-(+)-flutriafol. Taken together, this study indicated that a_w and temperature play important roles in regulating DON biosynthesis in F. graminearum with flutriafol enantiomers.

Free and Substrate-Immobilised Lipases from Fusarium verticillioides P24 as a Biocatalyst for Hydrolysis and Transesterification Reactions

Fungal enzymes are widely used in technological processes and have some interesting features to be applied in a variety of biosynthetic courses. Here, free and substrate-immobilised lipases from Fusarium verticillioides P24 were obtained by solid-state fermentation using wheat bran as substrate and fungal carrier. Based on their hydrolytic and transesterification activities, the lipases were characterised as pH-dependent in both reactions, with higher substrate conversion in an alkaline environment. Thermally, the lipases performed well from 30 to 45 °C, being more stable in mild conditions. Organic solvents significantly influenced the lipase selectivity using different vegetable oils as fatty acid source. Omega(ω)-3 production in n-hexane achieved 45% using canola oil, against ≈ 18% in cyclohexane. However, ω-6 production was preferably produced for both solvents using linseed oil with significant alterations in the yield (≈ 79% and 49% for n-hexane and cyclohexane, respectively). Moreover, the greatest enzyme selectivity for ω-6 led us to suppose a lipase preference for the Sn1 position of the triacylglycerol. Lastly, a transesterification reaction was performed, achieving 90% of ester conversion in 72 h. This study reports the characterisation and use of free and substrate-immobilised lipases from Fusarium verticillioides P24 as an economic and efficient method for the first time.

Nanoarmoring: strategies for preparation of multi-catalytic enzyme polymer conjugates and enhancement of high temperature biocatalysis

We report a general and modular approach for the synthesis of multi enzyme-polymer conjugates (MECs) consisting of five different enzymes of diverse isoelectric points and distinct catalytic properties conjugated within a single universal polymer scaffold. The five model enzymes chosen include glucose oxidase (GOx), acid phosphatase (AP), lactate dehydrogenase (LDH), horseradish peroxidase (HRP) and lipase (Lip). Poly(acrylic acid) (PAA) is used as the model synthetic polymer scaffold that will covalently conjugate and stabilize multiple enzymes concurrently. Parallel and sequential synthetic protocols are used to synthesise MECs, 5-P and 5-S, respectively. Also, five different single enzyme-PAA conjugates (SECs) including GOx-PAA, AP-PAA, LDH-PAA, HRP-PAA and Lip-PAA are synthesized. The composition, structure and morphology of MECs and SECs are confirmed by agarose gel electrophoresis, dynamic light scattering, circular dichroism spectroscopy and transmission electron microscopy. The bioreactor comprising MEC functions as a single biocatalyst can carry out at least five different or orthogonal catalytic reactions by virtue of the five stabilized enzymes, which has never been achieved to-date. Using activity assays relevant for each of the enzymes, for example AP, the specific activity of AP at room temperature and 7.4 pH in PB is determined and set at 100%. Interestingly, MECs 5-P and 5-S show specific activities of 1800% and 600%, respectively, compared to 100% specific activity of AP at room temperature (RT). The catalytic efficiencies of 5-P and 5-S are 1.55 × 10-3 and 1.68 × 10-3, respectively, compared to 9.11 × 10-5 for AP under similar RT conditions. Similarly, AP relevant catalytic activities of 5-P and 5-S at 65 °C show 100 and 300%, respectively, relative to native AP activity at RT as the native AP is catalytically inactive at 65 °C The catalytic activity trends suggest: (1) MECs show enhanced catalytic activities compared to native enzymes under similar assay conditions and (2) 5-S is better suited for high temperature biocatalysis, while both 5-S and 5-P are suitable for room temperature biocatalysis. Initial cytotoxicity results show that these MECs are non-lethal to human cells including human embryonic kidney [HEK] cells when treated with doses of 0.01 mg mL-1 for 72 h. This cytotoxicity data is relevant for future biological applications.

The Lid Domain in Lipases: Structural and Functional Determinant of Enzymatic Properties

Lipases are important industrial enzymes. Most of the lipases operate at lipid–water interfaces enabled by a mobile lid domain located over the active site. Lid protects the active site and hence responsible for catalytic activity. In pure aqueous media, the lid is predominantly closed, whereas in the presence of a hydrophobic layer, it is partially opened. Hence, the lid controls the enzyme activity. In the present review, we have classified lipases into different groups based on the structure of lid domains. It has been observed that thermostable lipases contain larger lid domains with two or more helices, whereas mesophilic lipases tend to have smaller lids in the form of a loop or a helix. Recent developments in lipase engineering addressing the lid regions are critically reviewed here. After on, the dramatic changes in substrate selectivity, activity, and thermostability have been reported. Furthermore, improved computational models can now rationalize these observations by relating it to the mobility of the lid domain. In this contribution, we summarized and critically evaluated the most recent developments in experimental and computational research on lipase lids.

Isolation and characterization of novel thermophilic lipase-secreting bacteria

The purpose of the present study was to screen and identify the lipase-producing microorganisms from various regions of Iran. Samples collected from hot spring, Persian Gulf, desert area and oil-contaminated soil, were analyzed for thermophilic extracellular-lipase producing organisms. Six strains with high activity on rhodamine B plates were selected for chemical identification and further study. Among these isolated bacteria, four strains show higher activity in pH-Stat method at 55 °C. These strains were identified by PCR amplification of 16s rRNA genes using universal primers. Fermentation increased the activity up to 50%. The growth medium, designed for lipase production, increased the activity up to 4.55 folds. The crude supernatant of ZR-5 after fermentation and separation the cells, was lyophilized and the activity was measured. Total activity of this strain was 12 kU/g that shows its potential for industrial uses. Further study is required for purification of enzyme and calculation its specific activity. Immobilization is another approach should be considered.

Lipolytic system of the tomato pathogen Fusarium oxysporum f. sp. lycopersici

The lipolytic profile of Fusarium oxysporum f. sp lycopersici was studied by in silico search and biochemical enzyme activity analyses. Twenty-five structural secreted lipases were predicted based on the conserved pentapeptide Gly-X-Ser-X-Gly-, characteristic of fungal lipases, and secretion signal sequences. Moreover, a predicted lipase regulatory gene was identified in addition to the previously characterized ctf1. The transcription profile of thirteen lipase genes during tomato plant colonization revealed that lip1, lip3, and lip22 were highly induced between 21 and 96 h after inoculation. Deletion mutants in five lipase genes (lip1, lip2, lip3, lip5, and lip22) and in the regulatory genes ctf1 and ctf2 as well as a Δctf1Δctf2 double mutant were generated. Quantitative reverse transcription-polymerase chain reaction expression analyses of structural lipase genes in the Δctf1, Δctf2, and Δctf1Δctf2 mutants indicated the existence of a complex lipase regulation network in F. oxysporum. The reduction of total lipase activity, as well as the severely reduced virulence of the Δctf1, Δctf2, and Δctf1Δctf2 mutants, provides evidence for an important role of the lipolytic system of this fungus in pathogenicity.

Purification, physico-chemical and kinetic properties of the deglycosylated Talaromyces thermophilus lipase

The Talaromyces thermophilus strain produces only one form of lipase called TTLI. When the culture medium was concentrated and stored at 4°C during a few days, we noticed the appearance of a second short form of lipase named TTLII. This second form was purified to homogeneity using gel filtration and FPLC-Anion exchange chromatography. The NH(2)-terminal 24 amino acid residues were found to be identical to those of TTLI. The treatment of the TTLI with endoglycosidase H decreased its apparent molecular weight from 39 to 30kDa which corresponds to the molecular weight of TTLII. This difference was mostly attributed to the N-glycosylation of the enzyme. In fact, the glycan chain content and concavaline A-Sepharose affinity column confirmed that the TTLII was completely deglycosylated. Compared to TTLI, the TTLII activity was completely decreased over a broad range of temperature and pH. Furthermore, the deglycosylation of the enzyme reduced its specific activity by 50% toward different substrates; strongly suggest that the N-glycans are determinants for optimal catalytic activity and thermal stability of this enzyme. Covalent immobilization of the enzymes on supports suggests the involvement of the glycan moiety in enzyme-polymer interactions. In the case of TTLI the glycan moiety can constitute an extra site for the covalent linkage of the enzyme on the carrier.